


Soulmates? Soulmates.

by misseshermionemalfoy



Category: The Mortal Instruments Series - Cassandra Clare
Genre: Alternate Universe - Soulmates, Explicit Sexual Content, F/M, Other Additional Tags to Be Added, Sibling Incest, Soulmate-Identifying Marks
Language: English
Status: In-Progress
Published: 2018-06-08
Updated: 2018-07-14
Packaged: 2019-05-19 14:41:25
Rating: Explicit
Warnings: Graphic Depictions Of Violence, Major Character Death, Underage
Chapters: 2
Words: 4,144
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14875697
Author URL: https://archiveofourown.org/users/misseshermionemalfoy/pseuds/misseshermionemalfoy
Summary: What would've happened if the kiss between Sebastian and Clary went differently in City of Glass? This is a soulmate AU where you can see color when you kiss your soulmate for the first time. Clary kisses Sebastian and realizes her world is full of color.





	1. Chapter 1

**Author's Note:**

> Obviously read with caution, sibling incest ahead

_ “That’s not true.” His hand came up and now he was cupping her face. His touch was gentle, almost tentative. “I’ve heard all about you, Clary. About the way you fought your father for the Mortal Cup, the way you went into that vampire infested hotel after your friend. Isabelle’s told me stories, and I’ve heard rumors too. And ever since the first one - the first time I heard you name - I’ve wanted to meet you. I knew you’d be extraordinary.”  _

 

_ She laughed shakily. “I hope you’re not too disappointed.”  _

 

_ “No.” He breathed, sliding his fingertips under her chin. “Not at all” He lifted her face to his. She was too surprised to move, even when he leaned toward her and realized, belatedly, what he was doing: Reflexively she shut her eyes as his lips brushed gently over hers, sending shivers through her. A sudden fierce longing to be held and kissed in a way that would make her forget everything else surged through her. She put her arms up, twining them around his neck, partly to steady herself and partly to to draw him closer.  _

 

Her eyes fluttered and for the first time in her life she saw color. The greenness of the trees, the creamy color of Sebastian’s skin. She nestled her fingers in his inky black hair and she let him pull her lip into his mouth. The earth seemed to stutter, as if it’s axis had been momentarily disrupted. But as soon as things started feeling strange they righted themselves just as quickly. As she blinked she saw color for the first time and it was so wonderful she leaned harder into the kiss. The world stuttered for a moment and she pushed the wrongness down. He sucked on her tongue lightly and she felt herself moan. Slowly, he backed away from her. “That was amazing.” He said breathily. 

 

“Can you… see color now?” 

 

“Yeah. It’s so bright… it’s lovely,” Sebastian said. 

 

“I think… I mean… doesn’t that mean we’re soulmates?” Clary asked him. 

 

“I guess so. I wasn’t expecting that.” Sebastian said earnestly. 

 

She stepped forward and wrapped her arms around him. “I’m so glad I met you.” She said lightly. 

 

He smiled, kissed her fiery red hair and said, “We should celebrate.” 

 

“Well... what about Jace?” Clary asked, wringing her hands nervously. 

 

“Oh… you both thought you were soulmates didn’t you?” 

 

“Yeah we did.” 

 

“But neither of you could see color could you?” 

 

“Nope.” She said pouting at him. “Jace is going to be broken hearted.” 

 

“We can get through it. I’m your soulmate we can make it work.” 

 

She smiled at him. Her eyes were glassy with unshed tears. Everything was so bright and beautiful. She wanted to touch everything. She had been counting on Jace being her soulmate. It was breaking her heart that he wasn’t. Still, here was this very pleasant, kind, boy standing in front of her telling her he held the keys to her heart. She rushed forward and held him close to her. “We’re going to be good together.” She said resolutely.

 

“I hope so.” He said charmingly back to her. She was still hugging him and when she pulled away she had tear tracks down her cheeks. He tilted her head up to his and kissed her eyelids. “I’m here and nothing is ever going to come between us.” 

 

She smiled tearfully and sniffled lightly. “Let’s head back. It’s getting late.” 

 

* * *

 

“So you kissed him… and you could see color?” Isabelle said joyfully. Clary nodded and wiped her eyes with another tissue. She was managing to hold it together for a pretty cry. “I just thought it would be Jace… I knew it was Jace but then… Sebastian came along.” 

 

“I’m sure you and Sebastian will be very good together. Aline speaks very highly of him.” Isabelle said confidently. 

 

“Do you you think he dyes his hair?” Clary asked Isabelle. 

 

“I don’t know, why?” 

 

“I got something black on my fingers when I put my hand on his hair.” 

 

“Maybe he does… what does it matter though? He’s your soulmate. He could be Ted Bundy and you’d still be destined to love him.” 

 

“Do you think it would be weird to sleep with him tonight? Like --- just sleep? I want to get to know him better. I’m destined to spend the rest of my life with him and I barely know him. And don’t say things like that!” 

 

“Fine, that’s probably a good idea. His room is upstairs, third door on the right.” Clary was already in her sleep shorts and an old t-shirt. 

 

Clary made her way upstairs and knocked on his door lightly. “It’s Clary.” 

 

“Come in!” Sebastian shouted. 

 

She opened the door and gasped lightly. Sebastian was standing there in a towel, water dripping off of him. He wasn't as thickly muscled as Jace but he was still all hard planes of muscle and bone. “I didn’t ---” 

 

“It’s quite alright. What’s up?” He ran a hand through his black hair. She stepped into the room and shut the door. 

 

“Would it be alright if we… slept in the same bed tonight? I don’t want to do anything, maybe just kiss. I just want to know you better.” Clary said a little distractedly. Sebastian was gorgeous without a shirt. 

 

“Of course. You want to do some pillow talk?” He fixed her with a very charming smile. 

 

She blushed faintly. “I’m a virgin, Sebastian.” 

 

He smiled kindly at her, “I wasn’t asking you to have sex with me Clary I would never ---” 

 

“I know… You’ve showed me such kindness since you’ve been here and I feel like I may have come off a bit frigid. I want to know you and love you but you’ve got to give a couple weeks before I really throw myself into this. Jace… well. Even if he’s my brother it was complicated between us before I found out and that was only a month or two ago. I want to love you with all my heart but you’ve got to let me drop my baggage at the door.” 

 

“Jace isn’t baggage, don’t say that.” Sebastian said kindly. “Let me get some clothes on and we can talk properly.” He went to the dresser and pulled out a pair of shorts and a clean t-shirt. He disappeared into the bathroom and she sat down on his bed. There were no pictures in the room, and very few personal items. It was kind of like Jace’s room in that way… she caught herself thinking about Jace and chided herself. Damn it. She was not going to let Jace ruin this for her. She took off her shoes and sat cross-legged on his bed. 

 

He came out and smirked at her. “You’re sitting on my side of the bed.” 

 

“Oh.” She popped up and switched sides. 

 

Sebastian turned off the big light and dimmed the bedside lamps. He got into bed, and reached out his hand for her. “I don’t bite.” 

 

“I know.” She laid down with him and pulled up the covers to her waist. She reached her hand out to him. It was a pretty big bed so she didn’t have to be too close to him. He held her hand and scooched up the covers onto his waist. 

 

“So what did you want to know?” Sebastian asked Clary. 

 

“Well what are your hobbies? I don’t know, anything you want to tell me, honestly.” She said. 

 

“Well, I don’t really have ‘hobbies’ but I train a lot. Throwing knives are my weapon of choice.” He squeezed her hand and asked, “What about you, growing up mundane you must have done more interesting things than training?” 

 

“Yeah, I draw and paint. My mother taught me.” Clary was reminded forlornly that her mother was still in a coma in New York.  

 

Sebastian turned on his side to face her. “I’d love to see what you’ve drawn some day.” 

 

“Yeah, maybe someday. I’m not very good…” Clary whispered. 

 

“Shh, I’m sure all your drawings are wonderful.” Sebastian said sweetly. 

 

She flushed slightly, “You’re so sure of me.” 

 

“Of course I am. Do you have a soulmate mark now?” 

 

“A what?”

 

“It’s a mark you get on your wrist… it’s kind of grim actually. It’s a timer until when your soulmate will die.” He showed her his wrist. His had 70 years, 3 months, 23 days, 47 minutes and 12 seconds left on it. 

 

She looked at her wrist and didn’t see anything at first in the dim light. “Could you turn the lights on a bit brighter, there’s something there but I can’t really see it.” 

 

He flicked the lights on bright and she looked at her wrist. There were three faint question marks on her wrist. “What does that mean?” Clary asked him. 

 

“I don’t know.” He swallowed hard. “Let’s hope I’m not going to kick the bucket anytime soon.”

 

“I hope not.” Clary said solemnly. 

 

“Can I have a kiss?” Sebastian asked Clary. 

 

“Mhmm.” She cupped his face and dipped her head down. She brushed her lips against his and breathed in his air as he breathed in hers. The result was dizzying and she felt a flush cover her cheeks and chest. She sank her lips down onto his and kissed him with force. Everything she was feeling about Jace not being her soulmate was making her feel reckless. She wanted to be held and kissed in such a way she would forget Jace. She moved from her spot on Sebastian’s bed and into his lap. 

 

He pulled away from her though. “Hey, hey.” He said holding her chin between his thumb and forefinger. “I’m not going anywhere you don’t have to kiss me like I’m going to evaporate. I want to take my time with you.” 

 

She flushed scarlet. He must know exactly what she was doing, trying to forget Jace. “O-ok.” 

 

“You’re going to regret it if we move too quickly. We have 70 something years to get to know each other.” 

 

“I just ---” 

 

“Want forget Jace ever existed?” 

 

“Yeah, that.” She hung her head in shame, she didn’t want him to think she was a slut… 

 

“Look at me Clary.” He said softly. 

 

She tilted her head up. “I’m sorry… It’s just been such a shock.” 

 

“I know, I wasn’t expecting this either.” Sebastian replied. 

 

“You like me though?” Clary asked Sebastian. 

 

“Of course I like you, don’t be silly. I wouldn’t have asked you to come with me on Wayfarer and kissed you.” 

 

“Please make me forget him. I don’t want to think about Jace anymore. Not when I’m with you. I want to love you.” 

 

She was still sitting on his lap and she was vaguely aware that this would be a very compromising position if they were caught like this. Jia Penhallow wasn’t likely to come home anytime soon though. He kissed her, and again she was struck with just how  _ right _ it felt to her. He kissed her deeply, pressing their lips impossibly close and opened her mouth to him with his thumb. She felt like she was sinking and flying all at once. He made her feel like she was light as feather and she was just drifting down to earth. She thought then, that she could love him. Not a forced kind of love, no, but a genuine, shining kind of love. She felt her heart sing in her chest as he wrapped his fingers in her thick, long hair. He sucked on her tongue again, as he had done earlier today and it garnered him another moan. He sucked a little harder then pulled back. 

 

“Remember you just wanted to sleep?” Sebastian reminded her. 

 

“Oh… right.” 

 

“Aren’t you tired, honey?” Sebastian asked. 

 

It had been getting late when they got back and now it had to be close to midnight. “C’mon we can talk more over breakfast.” 

 

“Ok, that sounds nice.” Clary said, climbing off his side of the bed and under the covers. She gripped his hand in hers. “Good night, my soulmate.” 


	2. Chapter 2

**Summary for the Chapter:**

> the demon towers go out... hmmm

Clary woke up to being curled up in the crook of Sebastian’s arm, their legs tangled and Sebastian’s hand on the flat of her stomach. She looked up at the clock, it was just past 8. She liked this, waking up with someone she knew she was going to spend the rest of her life loving. “Good morning,” she heard Sebastian say. She almost jumped, she didn’t think he was awake. 

 

“It’s still early. What are you doing awake?” 

 

“Early? This is sleeping in for me. I try to be up by 6:30 every morning.” 

 

“Damn, shadowhunters…” Clary lamented. 

 

“Yeah, I know, saving the world every day is rough,” he said and laughed lightly. 

 

“Sarcasm is the lowest form of wit, Babe.” 

 

“I didn’t realize we were on pet name terms,” Sebastian said with a smirk. 

 

“You’re my soulmate, we kind of need to be on pet name term,” Clary replied, matter-of-factly.

 

“Ok. Are you going to tell Jace today?” Sebastian asked her. 

 

She sighed. She didn’t want to tell him. She didn’t want to break his heart like that, but she knew, in this case especially, the truth would set her free. She wanted to break it to him gently. “Yeah, I can do that.” 

 

Sebastian was beginning to disentangle their limbs. “Whatever happens, just come find me afterward. I’ll be there for you.” 

 

“Ok, thanks.” 

 

Clary crawled out of bed and started her day. 

 

*~*~*

 

It was late afternoon, and the autumn sky was filled with the pink light of the setting sun. She had made plans to meet Jace in the Penhallows garden which was now filling with fallen leaves. She was running late, though. Isabelle had been chatting with her and it was now almost 5 in the evening. She saw Jace pacing and ran to him with a hug. He held her in his arms for a second and then let her go. “What did you need to talk to me about so urgently?” 

 

She remembered their fight and how he’d said horrible things about her. She remembered the kiss with Sebastian and how everything had seemed so light, and now she was looking at him, knowing she was about to break his heart. “I met someone.” 

 

“What do you mean you met someone?” Jace said, folding his arms across his broad chest. 

 

“I mean, I met my soulmate.” She said guiltily. She didn’t know why this mattered. Jace was her brother. “I know this is just going to make you hate yourself more, or whatever you want to call yesterday, but it’s Sebastian. Sebastian Verlac is my soulmate. Please be happy for me.” 

 

He smiled, but it didn’t reach his eyes. “Good, then that can be the end of whatever...” he gestured between them, “...this was. Soulmates are forever. I hope he’s good to you.” 

 

“He’s a complete gentleman,” Clary said. She was biting the inside of her cheek and she could almost taste blood. She was attempting not to cry. “You’re sure you’re not angry with me?” 

 

“Oh, I’m sure.” He was looking off in the distance, toward the Demon Towers. She thought he might be trying not to cry as well. There was a faint red light in the sky, the Demon Towers had begun to flicker. They went out completely a moment later. “Did the  Demon Towers just go out?” Jace asked Clary. 

 

“I think they did… what could cause that?” 

 

“I dunno, but we better get inside. The city will be in trouble if they stay out. Valentine could attack the city.” 

 

“Do you think that’s likely?” 

 

“With Valentine, you never know.” They headed inside and went to the Penhallows living room. It was just Isabelle and Alec there.

 

*~*~*

 

Alec and Isabelle were gathered by the living room window of the Penhallow’s house. As Clary walked in with Jace, she looked nervous and afraid. “What’s going on, guys?” 

 

“Someone’s taken the wards down with demon blood,” Isabelle said. Clary looked through the window and saw Angel Square on fire. The fountain in the center seemed to be pouring black demon blood instead of water. Several Drevak demons slouched past the window. She wished Sebastian was there to protect her. Still, she had Alec, Isabelle, and Jace, all of whom were more than capable of keeping her safe. 

 

“This is horrible!” Clary said harshly under her breath. 

 

“To the weapons room!” Alec said. 

 

They all darted down the hall and started getting on gear and arming themselves. Clary grabbed a seraph dagger and named it “Michael”. It took them several minutes, but soon they were armed to the teeth, excluding Clary, who just had the seraph dagger and a pair of brass knuckles. What, exactly, was she supposed to do in battle? She was more of a liability than anything else. It wasn’t fair to the rest of the group that she would keep them protecting her instead of protecting the city. “Should I just stay here?” Clary asked to the room at large. 

 

Jace looked annoyed. “Yes. You should stay here and be devoured by demons,” he said sarcastically. 

 

“Shut up Jace!” Izzy said. 

 

“Ready?” Alec asked them. 

 

They rushed down the stairs and into the square. A behemoth demon was attacking Aline. Jace tossed a throwing star, and Alec shot at it with runed arrows. Behemoth demons were well known for how difficult they were to kill. Jace ran up to it and began hacking at the demon with a broadsword. Izzy dispersed with Alec to go fight off more demons polluting Angel Square. 

 

Clary was alone for a moment before a pair of Hellhounds came upon her. The dogs snapped at her. She didn’t know what to do… how was she supposed to defend against these creatures? She had no training. 

 

Out of the corner of Clary’s eye, she caught a glimpse of a figure jumping from rooftop to rooftop and finally somersaulting down to the ground to face her. It was Sebastian. He had a gigantic sword in his hands. It was made of gold and adamas, the length of the sword glinted with morningstars. Sebastian hacked at the Hellhounds and they disappeared leaving a scorch mark on the pavement and the stink of demons. She swallowed hard. She’d never seen anything like what Sebastian had just done. “Where were you?” she said heavily, “I was scared.” 

 

“I know,” Sebastian said. He was covered in a thin sheen of sweat, presumably from hopping the rooftops.

 

In front of them, Jace was hacking madly at the Behemoth demon and it looked like he was nearly exhausted. “Please, go help my brother,” Clary said to Sebastian. He grinned mischievously and sprung into action. 

 

He vaulted into the air and stabbed one of the pieces of the slimy demon with his sword. Jace was looking pretty bad. He was covered in demon poison and ichor. Sebastian seemed to have boundless energy and he finally made the demon disappear with a crack of the air. The Behemoth demon vanished into its home dimension. Jace needed an iratze before he did anything else. Clary rushed to him and applied a healing rune with her stele. He came back to himself pretty quickly. “That was a rush,” he said with a smirk. 

 

Sebastian was off killing another one of the Behemoth demons and saving Izzy from a Hellhound. “Jace, you can’t get yourself killed. I need you around!” she said harshly. 

 

“I’m fine, Clary,” he responded resolutely. 

 

She let Jace go, and he unleashed his full wrath on the demons in the area. As Sebastian regrouped after killing a Ravener demon, she pulled him aside. “I’m scared, Sebastian! What if my soulmate mark means that you’re going to die tonight?” 

 

“Everything is fine, Clary. I think we should head down to the lake, though. Unless I’m very much mistaken, the mirror is Lake Lyn and Valentine is going to raise the angel at any time.” 

 

“How’d you know?” Clary asked suspiciously. 

 

“There’s nothing else, no space that would be big enough to raise an angel in Idris. That’s why. The Angel is like 60 feet tall.” 

 

“What!?” Clary was shocked. He sounded like he was onto something. “Get Jace! We’ll need him.” 

 

Sebastian got Jace, and they started winding their way down to the lake. 

 

*~*~*

 

When they were maybe 10 feet from the lake, Jace let out a loud gasp. Clary turned around to see Valentine standing there holding the dagger lodged directly in Jace’s shoulder.    
  


Jace ripped the knife out and tossed it to Clary. She caught it and marched forward. Valentine put his hands up in surrender. “Don’t kill your own father, how could you possibly live with that?” Valentine asked his daughter, but he reached for a dagger, readying himself to kill his daughter. 

 

“Like this!” She swiped out with the dagger and it grazed Valentine’s cheek. 

 

He laughed lightly, “Not the warrior woman your mother was, are you?” 

 

Clary swore and punched him square in the nose. He stumbled back and Clary advanced. She picked up a rock and bashed it against his cheek. His whole head bounced back from the attack. 

 

Valentine was wearing a thick leather gear jacket but that didn’t deter Clary from stabbing her father in the chest as if she was sticking pins in a pin cushion. Tears began to stream down her face and she thought of Jace’s face when Valentine stabbed him. She slit Valentine’s throat, and arterial spray covered her clothes, and Jace and Sebastian’s clothes. 

 

When it was over, Clary rushed to Jace and checked his shoulder. She was crying, hard. “Can you move your arm?” She asked Jace. 

 

Sebastian ran over. 

 

Jace was looking around as if he was in a lot of pain but otherwise unharmed. 

 

“Let me give you an iratze,” Clary said, sucking in shuddering breaths of air. “Valentine stabbed you and I killed him for it.” 

 

This seemed to wake up Jace from his stupor. “You killed Valentine?” 

 

“He almost killed you, Jace!” Clary said harshly.

 

“I know, I know. I’m not mad but, damn, you killed your own father.” 

 

“Are you ok?” Clary asked, fussing over him a bit. 

 

Jace stood up and dusted himself off. “I’m fine.” 

 

Clary stood up with the help of Sebastian. The Demon Towers were lit up again. 

 

Clary walked back to her father’s body and looked down at Valentine, whose eyes were still open. 

 

“Ave atque vale,” Clary said under her breath. 

 

“Hail and farewell,” Jace and Sebastian both said. 

 

“Let’s go and check on the others.” 

 

*~*~*

 

They found Max lying on the couch at the Penhallows with the toy soldier in his hand. Clary and Sebastian made themselves scarce as the Lightwoods grieved. 

 

*~*~*

 

It was well past midnight when Sebastian brought Clary up to his room. Clary changed into a pair of Sebastian’s shorts and an old t-shirt of his. Sebastian was in boxers and a t-shirt. 

 

They both had bruises and bumps from today, Clary more so than Sebastian. She winced as he looked at a bad gash from the Hellhounds. “It needs to be cleaned before I can heal it, Babe.” 

 

“Ok.” She looked around. She was biting her cheek because it hurt so badly, but she didn’t want to call out in pain or cry. 

 

Sebastian got out his wound-cleaning supplies. She winced as he put rubbing alcohol on a cloth and dabbed it on the wound. “It hurts,” she said, her bottom lip wobbling. 

 

“Shhhh,”  Sebastian said gently. He drew an iratze, she sighed with relief as a fresh and tender layer of skin closed over the wound. 

 

“What about you?” she asked him. “My rune power makes my runes more powerful, so I could probably give you an iratze to cover everything?” 

 

He took off his shirt so she could give him a few iratzes. There was a pattern of teeth marks burned into Sebastian’s back. 

 

“How’d you get these?” 

 

“I got them from the Behemoth demon. He got me with his teeth right before I killed him.” 

 

“Hasn’t it been hurting you this whole time?” Clary asked as she inked in several iratzes over Sebastian’s shoulders. 

 

“Yes, but there were more important things to attend to than demon bites.” 

 

“I guess so. Still, you should have told me…you were really brave today.” 

 

“So were you,” he said, pressing a kiss to her fiery red hair. 

 

“I’m exhausted,” Clary sighed. She collapsed into bed. Sebastian put away the medical supplies and climbed in next to her. 

 

“Do you think you’ll lose any sleep over it? Killing your father?” 

 

“He would have killed me if I hadn’t.” 

 

Sebastian reached down and held her hand under the covers. 

 

They fell asleep holding hands and, no, Clary didn’t lose a wink of sleep over Valentine. 


End file.
